This invention relates to film processing apparatus and, more particularly, to an improved multipurpose film handling cassette for exposing, processing and projecting images of photographic film.
Multipurpose photographic cassettes have been developed for use in motion picture photographic systems capable of processing an exposed strip of photographic material to a viewable condition as illustrated and described in such prior references as U.S. Pat. No. 3,615,127 issued to Edwin H. Land on Oct. 26, 1971; U.S. Pat. No. 3,623,417 issued Nov. 30, 1971 to Vaito K. Eloranta; and U.S. Pat. No. 3,748,994 issued July 31, 1973 to Joseph A. Stella, all of which are owned by the assignee of the present invention.
In such systems, use is made of a film handling cassette within which the several operations of exposure, chemical processing, drying and projection of the recorded images are accomplished without transferring the film from the cassette. In this arrangement, the strip of photographic film contained in the cassette can be exposed in a camera adapted to receive the cassette and then processed to provide viewable images by placing the cassette in a viewing apparatus equipped to activate the cassette-contained processor upon rewinding the exposed film strip. After processing in this manner, the viewing apparatus is operated as a projector to advance the film incrementally frame by frame past a light source for viewing of the recorded images.
In this arrangement, the unexposed photosensitive strip, initially wound upon a supply reel, preferably passes from the supply reel through a normally inoperative processing station and then across an opening of the cassette which functions at different intervals as both an exposure and projection station. Beyond the exposure station, the film is wound onto the takeup reel.
When substantially the entire length of the photosensitive strip in the cassette has been exposed and wound onto the takeup reel, the cassette is then loaded into a special purpose projector in which the motion of the film is reversed, this time passing from the takeup reel onto the supply reel. In its movement in this reverse direction, the film strip actuates the normally inoperable processing station so that the film strip is subjected to processing treatment in which a thin layer of processing fluid is supplied to the portion of the film emulsion intermediate the film margins by means such as, for example, a doctor blade in communication with and supplied with processing fluid passing through a nozzle communicating with a processing fluid reservoir. Immediately following the fluid deposition, in response to further film advancement, a valve member is actuated to move into blocking engagement with the processing fluid nozzle accordingly terminating further passage of processing fluid from the reservoir. Following a predetermined delay period, the film bearing the still wet layer of processing fluid is then again advanced through the exposure-processing station for projection and to complete drying of the film.
It can be appreciated that following the deposition of the processing fluid layer upon the film and prior to advancement of the still wet film strip through the exposure-processing station for the initial projection and drying operations that it is critical that the flow of processing fluid through the nozzle be completely and positively terminated immediately following deposition of the processing fluid upon the film strip. As briefly set forth above, in prior designs, incorporated in the processor is a slideable nozzle valve which is utilized to close off the processor nozzle and thereby disable the processor immediately following treatment of the film strip with the processing fluid. In relation to the nozzle opening, the valve is positioned initially in front of the nozzle opening in terms of film strip travel during rewind, i.e., during deposition of processing fluid. Additionally, a pressure pad component is positioned beneath the nozzle opening in a position such that a film engaging surface on the pressure pad is directly under the nozzle opening to thereby retain and interpose incremental portions of the film strip firmly against the under surface of the fluid applicator housing.
Following the processing operation and responsive to engagement by a film discontinuity or the like, located at the leading or takeup end of the film strip, the valve member is moved from its initial position so that it underlies and blocks the nozzle opening. Further, during this displacement of the valve, the pressure pad is cammed downwardly away from the film strip by side cams of the valve so as to deactivate the pressure pad and to free the film strip for unrestricted travel in either direction for subsequent projection and rewind cycles.
Accordingly, the valve member which is adapted to slide readily from its initial position to its processor disabling position serves not only to shut off the flow of processing fluid from the processor, but also serves the important function of displacing the pressure pad, which performs a critical function in spreading the desired processing fluid layer upon the film strip, during the processing operation, into a position where it will not interfere with the film strip travel once the processing has been accomplished. Accordingly, it will be appreciated that it is extremely important that the slide valve be accurately located and that premature release of the valve not occur prior to the time it is caused to move from its initial position into sealing engagement with the processing fluid nozzle.
One prior art approach to retaining the slide valve in its initial open position has been the use of a frictionally engaging member or the like such as is illustrated in U.S. Pat. No. 3,938,885, "Multipurpose Audiovisual Cassette System" of D. T. Scholz. Such an arrangement, however, has been found inadequate to retain the valve in its initial position during rough handling, for example, should the cassette be dropped prior to exposure and processing of the film strip.
Other approaches to retaining the slide valve in its initial open position are described in copending U.S. patent application Ser. No. 729,390, filed Oct. 4, 1976 by J. A. Stella, entitled "Photographic Cassette Having Pressure Plate Release of a Processor Disabling Valve" and in copending U.S. patent application Ser. No. 729,389, filed Oct. 4, 1976, by F. M. Czumak, entitled "Photographic Cassette Having Pressure Plate Release of a Processor Disabling Valve." In each of the above-identified applications, means are provided for preventing displacement of the valve member at all times prior to movement of the multipurpose cassette's pressure plate to the position it occupies during high speed continuous advancement of the film. In each of the described embodiments of these applications, physical contact is present between the slideable valve member and the pressure plate. In such cassettes, the slideable valve member also serves, in conjunction with a pair of electrical contacts located in the cassette, to provide an indication to the viewing apparatus as to the processed or unprocessed condition of a cassette inserted therein. The contact between the slide valve and the pressure plate results in electrical continuity between the two components and is considered to be undesirable. Electrical insulation between the pressure plate and the slide valve is of course possible, however, such a provision adds a step to the production costs and the risk of establishing electrical contact between the two due to insulation failure or the like still remains.